α-amylase is an enzyme capable of hydrolyzing starch into saccharides in vivo. If the activity of α-amylase can be suppressed, in vivo absorption of saccharides can be suppressed. Therefore, α-amylase inhibitors can be useful as effective components for food materials, tablets, and the like for diet and anti-diabetes purposes.
Fenugreek is an annual leguminous plant. Fenugreek seeds are known to have been used for long time for traditional spices such as curry powder.
Non-Patent Document 1 discloses an in vitro experiment using an extract extracted from a fenugreek powder with 30% ethanol. In the experiment, it was confirmed that such extract has an α-amylase inhibitory activity. However, the α-amylase inhibitory activity of the fenugreek powder described in Non-Patent Document 1 was not at a satisfactory level.
Meanwhile, Non-Patent Document 2 describes that when fenugreek saponin is ingested by a dog, saponin is decomposed into aglycon in the digestive tract so as to be excreted, and that when saponin is treated with β-glucosidase, a saccharide at position 26, but not a saccharide at position 3, is released from saponin. However, Non-Patent Document 2 does not describe any α-amylase inhibitory activity.    Non-Patent Document 1: Mol Cell Biochem. 2006 January; 281(1-2):173-83. Biochemical study of the anti-diabetic action of the Egyptian plants Fenugreek and Balanites    Non-Patent Document 2: Lipids. 1991 March; 26(3):191-7. Implication of steroid saponins and sapogenins in the hypocholesterolemic effect of fenugreek